Current art magnetic stripe readers and writers use conventional magnetic heads where reading or writing occurs when the magnetic stripe moves along the head's air gap while the magnetic remanence transitions are converted to voltage in the head's coil (reading) and the magnetic induction at the air gap, strong enough to overcome the magnetic stripe's coercivity, creates a new remanence pattern (writing). While writing, the rate of change of the induction in the air gap in conjunction with the relative linear velocity between the head and the magnetic stripe determine the data density on the magnetic stripe. This density and the data's magnetic format are prescribed by industry standards for different data tracks on the magnetic stripe cards.
Consequently, card writing machinery has been carefully developed with precision moving parts so that data density and data format are maintained within the allowable prescribed tolerances. Most magnetic stripe card writers also read the card for content verification.
Magnetic stripe readers are less complex then writers in the sense that they can be swiped manually at a liberal range of speeds. The read circuitry synchronizes to the resultant variable data rate with the help of synchronization zeros on either end of the magnetic stripe.
Current art magnetic read and/or write heads wear-out as a consequence of repeated reading or writing that involves their abrasive swiping against the magnetic stripe material. The read or write performance deteriorates as a result of the wear and eventually fails altogether.
Current art magnetic stripe card readers require a card guiding slot of a certain length for stabilizing the swipe rate and, in this way, the magnetic stripe, while stationary, never encounters the read head. Magnetic stripe card writers are tasked to perform the more difficult task of maintaining the required data density. Both the reader and particularly the writer do not easily lend themselves to miniaturization for use in mobile devices.
FIG. 1 shows three layout examples of magnetic stripe domain segments using Aiken Biphase encoding standards. The first line shows all zeros consisting of pairs of domains of alternating polarity. The second line shows all ones consisting of alternating polarities of a single domain—twice the frequency of the zeros. The third line consists of a combination of ones and zeros (10100).
FIG. 2 shows current flowing through a conductor 4 (illustrated in cross-section) that generates a magnetic field 6 of strength H (around the conductor 4). The strength of the magnetic field H complies with the following expression:
  H  =      I    R  
I is the current in the conductor and R is the radius (distance) from the center of the conductor 4 to the location of interest where the magnetic field 6 H is measured. The direction of the magnetic field 6 H is clockwise as indicated by the arrows on the magnetic field lines 6, and corresponds to a current direction in the conductor 4 that is perpendicular to the page and flows in a direction from the viewer into the page.
As is further shown in FIG. 2, a thin magnetic stripe layer segment 2 is located in close proximity to the conductor 4. The flow through the conductor imposes a magnetic field with polarity of the North Pole (N) and South Pole (S), as indicated in FIG. 2. The SN poles illustrated in FIG. 2 constitute a magnetic domain; each track in the magnetic stripe layer includes a plurality of magnetic domains placed in a straight line. When the current direction is reversed in a direction from the page to the viewer, the direction of the magnetic field is reversed to counterclockwise, and so are the S and N polarities on the magnetic stripe (not shown). The magnetic field strength 6 must be intense enough to overcome the coercivity of the magnetic stripe 2 material. Since the magnetic field is proportional to the current in the conductor 4, it is necessary to reach a balance between the magnitude of the current pulse and the coercivity of the magnetic material. Once the magnetic polarity on the magnetic stripe 2 has been set by the current, the current flow can be stopped and the BR (Induction Remanence) imprint on the magnetic stripe will remain in that setting until reversed by a reverse current in the conductor 4 or by an external magnetic field that is strong enough to overcome the coercivity of the magnetic stripe 2. Thus, current impulses of the right magnitude and direction are sufficient to imprint data on the magnetic stripe material.
Note that it is desirable to minimize the magnitude of the current pulses so that current levels and their current driver design and production become achievable with no difficulty. However, the lower the coercivity of the magnetic stripe material, the more susceptible is the magnetic stripe to inadvertent modification by external magnetic fields.
In accordance with PCT/US 04/10951, there is provided a bi-dimensional or multi-dimensional conductor array that is proximate to the magnetic stripe that copes with the shortcomings of the hitherto known solutions. FIG. 3A illustrates a non-limiting embodiment of this aspect of PCT/US 04/10951 utilizing a matrix conductor array.
Thus, as shown, two substantially proximate conductors are associated with each domain, allowing a selection of each domain by the sum of currents within the two conductors. (As may be recalled from PCT/US 04/10951, two domains constitute a single bit). Therefore, the sum of two currents flowing in the same direction is designed to overcome the coercivity of the magnetic stripe for each domain, whereas each current alone or two opposing currents will not. In FIG. 3A, current through lines y2-y2 and x6-x6 that together become a higher total current at domain 100 is an example of such matrix domain selection. This approach is akin to the selection process of a single core in a magnetic core memory that allows the selection to be accomplished in the form of a matrix, and consequently uses fewer current drivers.
Thus, a matrix having A rows and B columns can support up to A·B entries, i.e. bits. For instance, in the case of 500 bits, 1000 domains are required and, thus, a 32 over 32 matrix can be employed so that any one of the 1000 domains (or up to 1024 domains) is controlled by a unique (i,j) entry. Accordingly, 64 lines are required to write any desired bit in the series of 500 bits.
Another matrix example is illustrated in FIG. 3B. This matrix is two-dimensional and reduces the number of necessary drivers in the same manner as the matrix described in FIG. 3A. However, the objective of this example is to emphasize a minimum number of conductors per bit. Consequently, a single conductor will be driven with enough current to overcome the coercivity of the magnetic stripe material, where the drivers y3 and x4 selectively drive conductor element 100. All drivers in this example are bidirectional and drive current in the direction dictated by the data content. This matrix example is important in cases where the technology reaches yield degradation at the range of high conductor densities.